At the moment the file transfer system is really unstable and it's essentially pure luck that it still works.
The original brief I worked to was just to make a queueing system to be used in the Mod Manager. I've had to hack it up to allow people to download from the server information page, and now from the loading page. Touching it too much can cause it to break sometimes and I haven't narrowed down why so I'd like to avoid people interacting with it when it has a direct influence on whether or not they are able to spawn in the server.
It'd be a nice feature to have in the future so you can manually choose which add-ons you want to skip. It'll definitely have to be a v4 feature though.
